Effects of different feeding frequencies on growth, cataract development and histopathology of lumpfish (Cyclopterus lumpus L.)

Under embargo until: 2020-11-13Three duplicate groups of individually tagged lumpfish (mean initial weight: 22.3 ± 2.5 g) were fed either daily (7DW); four days per week (4DW) or three days per week (3DW) at a feeding rate of 2% body weight day−1 for a period of 126 days. There were significant differences in growth rates between the groups with the 7DW fish having the highest growth rates. Cataract prevalence was 53% lower in the 3DW group compared to the 7DW group. Histological examination showed that in some individuals in all three groups there was moderate expansion of the lamina propria in the mid and hind gut regions of the intestine with tissue most likely to represent fibrous tissue with scattered leucocytes. The severity of inflammation appeared to increase the more frequent the fish were fed with the 7DW fish having the highest inflammation score in these tissues. Feeding fish daily also resulted in higher levels of liver vacuolisation and chronic inflammation of the lamina propria in the mid and hind gut region of the intestines. Results from the present study show that restricted feeding regimes can be used to control growth and improve gut and eye health in lumpfish.acceptedVersio

Comparison of diet composition, feeding, growth and health of lumpfish (Cyclopterus lumpus L.) fed either feed blocks or pelleted commercial feed

Two duplicate groups of individually tagged lumpfish (mean initial weight: 21.5 ± 3.2 g) were fed either a commercially available lumpfish feed or feed blocks for a period of 123 days. The aim was to evaluate and compare the effects of these feed types on growth, cataract development and histopathology in lumpfish. There were significant differences in growth rates between the groups with fish fed pelleted feed having the highest growth rates. The development of cataracts was significantly different with fish fed pelleted feed having a cataract prevalence of 87% at the end of the study period whilst fish fed with feed blocks had 10% prevalence. The results of the histological examination undertaken in this study showed overall small differences between the two dietary treatments. In some individuals in groups receiving both diets, there was mild to moderate expansion of the lamina propria with tissue most likely to represent fibrous tissue with scattered leucocytes. Overall, the findings of the present study show that lumpfish will readily graze from feed blocks and although growth is lower the prevalence of cataract is greatly reduced using feed blocks

Comparison of diet composition, feeding, growth and health of lumpfish (Cyclopterus lumpus L.) fed either feed blocks or pelleted commercial feed

Two duplicate groups of individually tagged lumpfish (mean initial weight: 21.5 ± 3.2 g) were fed either a commercially available lumpfish feed or feed blocks for a period of 123 days. The aim was to evaluate and compare the effects of these feed types on growth, cataract development and histopathology in lumpfish. There were significant differences in growth rates between the groups with fish fed pelleted feed having the highest growth rates. The development of cataracts was significantly different with fish fed pelleted feed having a cataract prevalence of 87% at the end of the study period whilst fish fed with feed blocks had 10% prevalence. The results of the histological examination undertaken in this study showed overall small differences between the two dietary treatments. In some individuals in groups receiving both diets, there was mild to moderate expansion of the lamina propria with tissue most likely to represent fibrous tissue with scattered leucocytes. Overall, the findings of the present study show that lumpfish will readily graze from feed blocks and although growth is lower the prevalence of cataract is greatly reduced using feed blocks

It works! Lumpfish can significantly lower sea lice infestation in large-scale salmon farming

To assess the efficacy of lumpfish grazing on attached sea lice on Atlantic salmon, six large-scale sea cages, (130 m circumference, 37,688 m3 volume) each stocked with approximately 200,000 salmon 0+ smolts, were stocked with a 4, 6 and 8% density (8000, 12,000 and 16,000, respectively) of lumpfish. The sea cages without lumpfish acted as controls. Sea lice infestation levels on the salmon were monitored weekly and bi-weekly from 6 October to 17 May the subsequent year. Mortality of the lumpfish rose with decreasing sea temperatures to around 0.8% week−1 and did not vary between the lumpfish groups. There were clear signs of lumpfish grazing on sea lice, with significantly lower average levels of chalimus, pre-adult and adult female Lepeophtheirus salmonis and Caligus elongatus sea lice per salmon. Lumpfish in the high density (8%) group reduced the mature female L. salmonis to levels equal to or lower than the counts recorded prior to the start of the study. Overall, the present results indicate that lumpfish are a suitable cold-water option for biological delousing of Atlantic salmon in large-scale production conditions

The use of photoperiods to provide year round spawning in lumpfish Cyclopterus lumpus

In order to provide year round spawning broodstock, lumpfish (initial size 746 g and 24.9 cm) were reared under four different photoperiod regimes from January 2017 to July 2018. One group was reared under simulated natural photoperiod (LDN, control group) for Tromsø (70°N). The second group was transferred to continuous light (LD240) on 30 January 2017 and reared at LD24:0 throughout the trial period. Two compressed and phase advanced photoperiods were also established. Both groups were moved from LDN to LD24:0 on 30 January 2017, and after that reared at compressed natural photoperiods where the annual photoperiod was compressed down to six months (L6) or nine months (L9) for the duration of the study. Spawning time was shifted in both compressed groups during both years of the study. Spawning activity in the second year of the study was higher and followed more closely the expected spawning period in the compressed and the LDN groups. Spawning in the LD240 group was spread out over the experimental period with no distinct peak in spawning. A seasonal and pronounced drop in condition factor was found for females in the L9, L6 and the LDN groups. This post-spawning loss in condition was closely related to the spawning activity of each group. The current findings suggest that photoperiod has a strong influence on the timing of lumpfish maturation and can be used as an efficient and inexpensive tool to secure lumpfish reproduction operations i.e. year-round supply of egg and milt and/or timing with optimal temperature regimes

The use of photoperiods to provide year round spawning in lumpfish Cyclopterus lumpus

In order to provide year round spawning broodstock, lumpfish (initial size 746 g and 24.9 cm) were reared under four different photoperiod regimes from January 2017 to July 2018. One group was reared under simulated natural photoperiod (LDN, control group) for Tromsø (70°N). The second group was transferred to continuous light (LD240) on 30 January 2017 and reared at LD24:0 throughout the trial period. Two compressed and phase advanced photoperiods were also established. Both groups were moved from LDN to LD24:0 on 30 January 2017, and after that reared at compressed natural photoperiods where the annual photoperiod was compressed down to six months (L6) or nine months (L9) for the duration of the study. Spawning time was shifted in both compressed groups during both years of the study. Spawning activity in the second year of the study was higher and followed more closely the expected spawning period in the compressed and the LDN groups. Spawning in the LD240 group was spread out over the experimental period with no distinct peak in spawning. A seasonal and pronounced drop in condition factor was found for females in the L9, L6 and the LDN groups. This post-spawning loss in condition was closely related to the spawning activity of each group. The current findings suggest that photoperiod has a strong influence on the timing of lumpfish maturation and can be used as an efficient and inexpensive tool to secure lumpfish reproduction operations i.e. year-round supply of egg and milt and/or timing with optimal temperature regimes.submittedVersio

The use of photoperiods to provide year round spawning in lumpfish Cyclopterus lumpus

In order to provide year round spawning broodstock, lumpfish (initial size 746 g and 24.9 cm) were reared under four different photoperiod regimes from January 2017 to July 2018. One group was reared under simulated natural photoperiod (LDN, control group) for Tromsø (70°N). The second group was transferred to continuous light (LD240) on 30 January 2017 and reared at LD24:0 throughout the trial period. Two compressed and phase advanced photoperiods were also established. Both groups were moved from LDN to LD24:0 on 30 January 2017, and after that reared at compressed natural photoperiods where the annual photoperiod was compressed down to six months (L6) or nine months (L9) for the duration of the study. Spawning time was shifted in both compressed groups during both years of the study. Spawning activity in the second year of the study was higher and followed more closely the expected spawning period in the compressed and the LDN groups. Spawning in the LD240 group was spread out over the experimental period with no distinct peak in spawning. A seasonal and pronounced drop in condition factor was found for females in the L9, L6 and the LDN groups. This post-spawning loss in condition was closely related to the spawning activity of each group. The current findings suggest that photoperiod has a strong influence on the timing of lumpfish maturation and can be used as an efficient and inexpensive tool to secure lumpfish reproduction operations i.e. year-round supply of egg and milt and/or timing with optimal temperature regimes